Research has shown that many elementary school children exhibit disruptive and aggressive behavior and that such behaviors are related to subsequent mental disorders and school failure. Educators and others working in schools have developed and implemented whole school interventions designed to decrease such behavior. Although many of these interventions are based on well-documented behavioral management practices, they have not been evaluated using the same outcome measures and rigorous research designs as interventions developed through NIMH funding sources. The Johns Hopkins University (JHU), the Maryland State Department of Education (MSDE), and Sheppard Pratt Health System (SPHS) and local school districts in Maryland have developed a partnership to study the effectiveness of the Positive Behavioral Interventions and Support (PBIS) strategy on reducing disruptive and aggressive behavior. PBIS is one of the most widely used whole school interventions designed to decrease disruptive and aggressive behavior. Specific aims for this project include: Aim 1. To determine if students in elementary schools randomized to the PBIS intervention are less likely to exhibit behavioral or emotional problems than students in schools randomized to the standard practice condition, and Aim 2. To identify other factors that affect the level of behavioral or emotional problems in school. PBIS training began in summer of 2002 with implementation in Fall 2002 for treatment schools in a first group of 24 schools. A second group of 28 schools will be recruited in spring 2003 and will be trained in summer 2003. Prior to training, schools will be stratified by school district, matched for similar demographic characteristics, and randomly assigned into one of two conditions: (1) training and implementation of PBIS (n=28), or (2) no training or implementation of PBIS (n=24). With preexisting funds, baseline assessments for all group 1 schools are underway. Each year of the study data will be collected: (a) teacher ratings of student classroom behavior and need for mental health services, (b) student ratings of school climate, (c) independent observations of student behaviors; (d) school characteristics and organizational climate, (e) implementation of the PBIS strategy, and (f) school records academic functioning and disciplinary and service referrals.